1. Field of the Invention
The present invention relates to an “insitu” method to repair underground pipes and conduits to reduce or eliminate ground water infiltration while stabilizing the proximate ground formation surrounding the pipes.
2. Background of the Invention
The Clean Water Act has mandated that ground water infiltration into our sewer systems be substantially reduced or eliminated. Many methods of repair have been devised over the last thirty years. Some of those repair methods include slip lining, pipe bursting, cured in place pipe lining (CIPP), fold and form thermoplastic lining, spot repairs, as well as the traditional dig and removal/replacement of pipelines.
It is a known fact that the federal interstate highway system has met and in certain cases exceeded its design life by controlling or reducing incidents of pavement collapse, settling and irregular surfaces. This has been achieved with the development of techniques for the injection of grouts or placement of epoxy patches. In addition, the concrete repair industry has developed and refined the utilization of expandable structural closed cell foams to raise, level and stabilize concrete slabs, foundations, pavements and buildings.
The “insitu lining” repair of pipes has been the most effective alternative to pipe “dig and replacement” for many year. Occasionally an existing annular space or void adjacent to the outside surface of the pipe or conduit has been injected with gelatinous grout materials to eliminate water infiltration into the pipe. This repair has been only temporary since the gelatinous material is not dimensionally stabile and often requires later replacement. The grout is not capable of stabilizing the ground around the pipe even if the entire annular space is filled with the gelatinous grout. The lack of stability and support can result in additional stress on the pipe structure, with eventual degradation of the pipe and resulting water infiltration.
Injection of expanding closed cell foams has seldom been used to repair pipes. Where the closed cell foams have been used to level or reinforce pipe sections, there has been migration of the foam into the pipe/conduit joint that, if left in place, can cause an occlusion or blockage. When this migration into the interior diameter of the pipe does occur, a cutting or grinding device must be inserted as a subsequent step to remove the excess foam.
Another issue is the typical foams being used today are polyurethane's which often contain isocyanate, a groundwater contaminant. Some research has been conducted to determine if the closed cell foam chemistry could be used with grout packers. The blowing agents in the foam, however, create a near immediate reaction that will not allow the annular space to be filled with the foam.
There are hybrid polyester/urethanes expandable closed cell foams that could be used and avoid isocyanate. However, these alternate foam formulations have not been well suited to curing in the ambient underground soil conditions.
Another method for repair of pipes has been to excavate a damaged pipe section and wrap the outer pipe wall with a high tensile strength material having an elasticity maintaining the band in contact with the pipe. See for example U.S. Pat. No. 4,700,752 of Norman C. Fawley. Another method has been to repair or reinforce a pipe section by wrapping the outer pipe wall with a composite material having a multiplicity of high tensile strength filaments encapsulated in a resin matrix. The wrapping material is manufactured in a coiled structure and installed by deflecting portions of the material into an uncoiled configuration and then wrapping those portions of the material around the pipe. The material may be applied with an adhesive coating on the pipe surface and between each coil layer. See for example Fawley, U.S. Pat. No. 5,683,529 and 5,677,046.
The measure of physical properties of materials relevant to the present invention include ASTM D1621 Compressive Strength, ASTM D790 Flexural Strength, ASTM D1622 Density, ASTM C 273 Shear Strength, ASTM D 2126 Dimensional Stability, ASTM D696 Coefficient of expansion, ASTM D 543 Chemical Resistance, and ASTM D 2842 Water Absorption.